This invention relates generally to the field of valves for controlling the flow of a fluid in a conduit or pipe; and more specifically to valves having a slideable gate for establishing the position of the valve in any one of a plurality of positions including and between a fully open position at which a maximum flow of fluid through the conduit in which the valve is placed occurs, and a fully closed position at which zero flow of fluid through the conduit in which the valve is placed occurs.
Specifically, a knife gate valve, using modular, interchangeable end components, and common body, internal and topworks components, that offers versatility for use in multiple applications, is disclosed.
Previously known knife gate valves have typically been of the wafer type, with standardized end-to-end dimensions, to allow for connection in flanged systems. Although this has been a widely accepted method of installing knife gate valves, it has several drawbacks. First, the use of a wafer type valve prevents the use of the valve in any system other than a flanged piping system, without the use of transition flanges on the mating piping. Second, installation time for a flanged system is considerably greater than for a grooved or threaded system. Third, the valve must be removed from the line in order to replace or repair the valve seats.
Accordingly, one object of the present invention is to provide a gate valve that incorporates flanges into the main body of the valve to secure one of a number of different modular end components to the valve, the end components being adapted to interface with other than flanged systems. This provides two benefits to the user. First, the user does not have to purchase or install transition flanges, thereby saving material and labor costs.
Second, valve installation time and labor cost are reduced from that required to install a flanged joint, to only that needed to assemble a joint compatible with the modular end component, such as a threaded, plain end, or grooved pipe joint. This can be a significant factor in situations such as in mining applications, where valve replacement is frequent and the need to minimize shutdown time is critical.
It is a further object of the present invention to provide a gate valve in which common internal components can be utilized with several different modular end component configurations. Internal components and topworks components of the gate valve of the present invention are designed to function as common parts, such that the same parts can be used regardless of the end components selected. In effect, the end components become interchangeable parts. Internal parts of the gate valve differ only between resilient seated and metal seated, as well as between metallic and non-metallic (e.g., plastic) versions.
A still further object of the present invention is to provide a gate valve that can be used, or easily modified for use, in multiple markets and in multiple types of systems. The modular end components supplied as part of the valve body can be provided with any of several pipe end configurations such as grooved, threaded, butt-weld, and plain end. Furthermore the modular end components can be fabricated from a variety of materials, such as ductile iron, steel, stainless steel, plastic and aluminum. This versatility allows the use of the valve in a wide variety of applications.
A still further object of the present invention is to provide a gate valve with maintenance, repair, and ease of seat replacement in mind. Seat repair, or replacement, requires the disassembly of the valve. However, the valve does not have to be removed from the line to achieve seat replacement. The valve is designed to be disassembled in line such that the end plates can be pulled back from the center plates, allowing, the seats and seat rings to be pulled from the assembly and replaced. Upon disassembly, the topworks bracket and operator remain attached to one end plate, with the gate in the open position, while the other end plate is free to move along the pipeline. The topworks bracket is slotted on both sides for the purpose of being able to easily remove the free cast end plate.
Yet another object of the present invention is to provide a gate valve that utilizes a pair of xe2x80x9ccup-shapedxe2x80x9d cast end plates, which abut against a common center plate, and are assembled using a common set of bolts, to house the valve internals (modular end components, seat rings, and seats).
Another object of the present invention is to provide a gate valve that is highly modular and is capable of being adapted to accommodate several different types of end connections by simply switching out only the end components, and in certain cases, additionally, the seats and seat rings.
Another object of the present invention is to provide a gate valve having a limited compression seat design, as well as means for accommodating volumetric displacement of the valve seats.
Another object of the present invention is to provide a gate valve, which utilizes plastic end components, especially polyethylene, in the valve body, in a pre-stressed and fixed dimension condition, to account for dimensional changes due to thermal changes and viscoelasticity.
Another object of the present invention is to provide a knife gate valve that is capable of being directly attached to plastic piping systems, especially polyethylene (PE) and polyvinyl chloride (PVC), by means of fusing, fusion welding, epoxy, or mechanically attaching via grooves, or other means.
Another object of the present invention is to provide a gate valve that provides direct access to plastic piping systems, by providing an internal diameter (i.d.) that directly matches the piping system i.d. and provides an uninterrupted flow path through the valve.
Another object of the present invention is to provide a gate valve that is capable of direct attachment to a grooved piping system, without the need for external attachment of a transition fitting.
Another object of the present invention is to provide a gate valve that can be disassembled and repaired in line.
Another object of the present invention is to provide a gate valve that has the capability for a xe2x80x9ccross-overxe2x80x9d connection at the valve using alternate modular end component types. For example, a valve could be provided with grooved metallic modular end component on one side of the valve, and a plain end plastic end modular end component on the opposing side. Another typical combination is the use of a grooved metallic modular end component on one side, with a plain metallic modular end component on the opposing side.
The present invention is based on a gate valve, particularly a knife gate valve, that incorporates modular end components into the main body assembly, and offers the ability to interchange the end components to allow the valve to be modified to match customer needs. The end configurations with which the valve can be supplied are virtually unlimited, and include grooved, plain end, threaded, and welded.
Ends can be supplied with rubber or polyurethane lining, and can be made from several materials including steel, iron, plastic (PE, PVC, PP, FRP, etc.), stainless steel, and aluminum.
The valve features a full round opening port. A resilient seated version is designed to be drop tight, and bi-directional. xe2x80x9cWettedxe2x80x9d parts are limited to the end components, the seats, and the gate in the full open and full closed positions. Upper support plates and brackets are designed to be versatile and are capable of accommodating several different types of commercially available actuators.
The assembly focuses on using matching end plates to house modular flange ends, seat rings, and seats. The design allows the modular ends to be attached within the assembly, without passing bolts through the flange. The interaction of the internal cavity, or cup shaped element of the end plate with the thickness dimension of the flange end, and the seat ring, controls the compression on the seats of the valve.
In its preferred embodiment the knife gate valve according to the invention has a flow path for fluid flow through the valve. The knife gate valve is attachable to pipe ends for integration into a piping network and comprises a knife gate having a planar surface oriented transversely to the flow path and movable within the valve transversely into and out of the flow path. A pair of guide plates are positioned along opposite edges of the knife gate for guiding its motion. The guide plates are substantially coplanar with the knife gate. First and second seals are positioned on opposite sides of the knife gate and the guide plates, the seals surrounding the flow path and sealingly engaging the guide plates. The seals are also sealingly engageable with the knife gate upon movement of the knife gate into the flow path and sealingly engageable with one another upon movement of the knife gate out of the flow path.
First and second elongated tubes comprising the modular ends are positioned coaxially with the flow path on opposite sides of the knife gate. Each of the tubes has a respective flange positioned at one end thereof, the flange extending radially outwardly therefrom. The one end of each of the tubes faces the knife gate, and each of the flanges has a first surface facing the knife gate which sealingly engages one of the seals. Each of the flanges also has a second surface opposite the first surface.
First and second end plates are positioned on opposite sides of the knife plate. Each of the end plates has a respective opening adapted to receive one of the tubes. Each of the end plates also has a respective surface surrounding the opening for engaging the second surface of one of the flanges of the tubes. The end plates are attached to the guide plates and capture the flanges and the seals therebetween. The tubes extend outwardly from the end plates in opposite directions and are attachable to the pipe ends. The knife gate valve also includes means for moving the knife gate mounted on the valve.
One of the tubes comprising the modular ends may have a circumferential groove positioned in spaced relation to an end opposite the flange, the groove adapting the one tube for attachment to the pipe end by means of a mechanical pipe clamp. The tubes and the flange on the tubes may be comprised of metal or plastic.
Preferably, the seals are comprised of an elastomeric material. First and second spacer rings are positioned on opposite sides of the knife gate coaxially with the flow path. The first spacer ring is between one of the flanges and the guide plates, and the second spacer ring is between another of the flanges and the guide plates. Each of the spacer rings has an inwardly facing shoulder respectively engaging and radially supporting one of the seals and preventing motion of the seals when the knife gate is moved relatively thereto.
Preferably, the seals comprise a first lobe extending circumferentially around the seal and positioned between one of the flanges and the spacer rings to effect a fluid tight seal therebetween. A second lobe is attached to the first lobe and also extends circumferentially around the seal, the second lobe being positioned radially inwardly of the first lobe and engaging one of the flanges. A sealing face extends circumferentially around the seal and is positioned opposite the second lobe for engagement with the knife gate. A displacement cavity is positioned between the first and the second lobes and extends circumferentially around the seal. With this configuration of seal the first lobes are compressed between the flanges and the spacer rings causing volumetric expansion of the sealing faces against the knife gate and the second lobes against the flange for effecting a fluid tight seal therebetween when the knife gate is in the flow path, the sealing faces of each the seal being otherwise compressed into sealing contact with one another when the knife gate is removed from the flow path.
Preferably, the spacer rings each have a respective predetermined thickness for establishing a desired compression of the first lobes between the flanges and the spacer rings and the sealing faces against the knife gate, the desired compression being achieved when the spacer rings respectively engage both the flanges and the guide plates thereby separating the flanges and the guide plates by the predetermined thickness of the spacer rings.
Preferably, the knife gate valve further comprises an aperture positioned between the guide plates substantially in the plane of the knife gate. The aperture is positioned at a lowermost point of the knife gate valve and is in fluid communication with the flow path for allowing solids in the flow path to pass outwardly from the knife gate valve through the aperture.